The present invention relates to a plug, also known as a xe2x80x9ccollarxe2x80x9d or an xe2x80x9canchorxe2x80x9d, such as the ones used for operatively connecting torsion springs to overhead shafts of counterbalancing mechanisms used for garage doors and the like, in order to allow a torque transfer between the torsion spring and the overhead shaft so as to counterbalance such cable-operated doors.
It is known in the art that large, vertical, cableoperated doors, such as commercial and residential sectional garage doors, usually require counterbalancing mechanisms to counterbalance the weight of the door in order to decrease the force required to open the door and also facilitate its closing from a raised to a lowered position. Large sectional garage doors used in commercial and residential applications may be manually or power operated. In either case, but particularly for manually operated doors, counterbalancing mechanisms have been used for many years to counterbalance the weight of the door and control its opening and closing movements so that one person can easily control the operation of the door. Counterbalancing mechanisms are also advantageous for power operated overhead doors since they reduce the power requirements needed for the motor and they lower the structural strength required for the door opening and closing mechanism. In other words, lighter weight, lower cost. door controlling mechanisms may be used if a counterbalancing mechanism is connected to the door to assist it in its opening and closing movements. Furthermore, the provision of a counterbalancing mechanism minimizes the chance of a rapid and uncontrolled closing of the door in the event of a failure of the door opening and closing mechanism, which can result in serious injury or damage.
It is also known in the art that a widely used type of counterbalancing mechanism generally comprises a pair of spaced apart cable drums connected to flexible cables. each cable being in turn connected to a lower opposite side edge of the garage door. The cable drums are usually mounted on a overhead shaft which is supported above the door opening and is connected to one or more torsion springs which are each fixed to the shaft at one end, and secured to a fixed structure such as the wall for example at the other end, so that the cable drums are biased to rotate in a direction which winds the cables onto the drums and counteracts the weight of the door connected to the cables. The torsion springs are adjusted to properly balance the weight of the door so that minimal opening and closing efforts are required, either manually or when motor controlled. An example of a conventional cable-operated door and its corresponding counterbalancing mechanism is shown in FIG. 1.
It is also known in the art that conventional, low cost adjustment devices used for the abovementioned type of counterbalance mechanism, and widely utilized in the garage door industry, are generally cylindrical xe2x80x9ccollarsxe2x80x9d commonly referred to also as xe2x80x9cplugsxe2x80x9d (or xe2x80x9cconesxe2x80x9d) which are connected to the so-called fixed ends of the torsion springs and are thus mounted on the aforementioned shaft for adjusting the deflection of the springs to preset the counterbalance force. The aforementioned collars usually include one or more setscrews which lock the collars to the shaft to prevent rotation thereabout except during normal adjustment of the spring deflection. The collars also usually include sockets for receiving winding bars whereby the springs are manually preset, or xe2x80x9cpreloadedxe2x80x9d, by rotating the collars with respect to the shaft using the winding bars and then locking the collars to the shaft with the setscrews. Each collar also may include a slot onto which a corresponding free end of the torsion spring is hrooked on. These slots are usually T-shaped,, and are thus commonly known as xe2x80x9cT-slotsxe2x80x9d. An example of a prior art T-slot collar is shown in FIGS. 2 and 3.
Presently, the T-shape of the slots of the plugs known in the art allows the introduction of the spring""s tail without the use of any tool. Once the spring tail is introduced into the T-slot of the collar, both the collar and the spring are then introduced onto a shaft and installed on site, after which the collar is pushed towards the spring and then rotated around the spring axis in order to have the spring tail blocked there by the T-slot collar. The combined slot and shaft hold the assembly together without any other accessories.
An important problem associated with the aforementioned type of counterbalancing mechanism, or with any other type of counterbalancing mechanism which uses collars (also known as xe2x80x9canchorsxe2x80x9d) having T-slots and tensioning springs, is that if the tail of the spring is too long, it will contact the shaft, and may eventually groove it to the point where the shaft may fail and cause personal injuries or render the counterbalancing mechanism Inefficient or inoperable.
Another important problem associated with the aforementioned type of counterbalancing mechanism, or with any other type of counterbalancing mechanism which uses conventional collars and tensioning springs, is that several of the plugs used in the industry do not allow a great number of total active spring coils to be used, since the first three to rive coils are generally used to maintain the spring onto the plug. An example of such plugs is shown in FIGS. 4 and 5.
Yet another important problem associated with the aforementioned type of counterbalancing mechanism, or with any other type of counterbalancing mechanism which uses collars having T-slots and tensioning springs, is the phenomenon known as xe2x80x9cclampingxe2x80x9d, an example of which is shown in FIGS. 6 to 9.
Yet another problem associated with the aforementioned type of counterbalancing mechanism, or with any other type of counterbalancing mechanism which uses collars having T-slots and tensioning springs, is that they are not devised to gauge the adequateness of the dimensions of the torsional springs mounted thereon.
Yet another important problem associated with the aforementioned type of counterbalancing mechanism, or with any other type of counterbalancing mechanism which uses winding collars having T-slots and tensioning springs, arises from the fact that the springs mounted thereon tend to xe2x80x9cwavexe2x80x9d due to extension and contraction.
Hence, in light of the aforementioned, there is a need for an improved device for operatively connecting torsion springs to overhead shafts of counterbalancing systems used for cableoperated doors, such as garage doors and the like.
The object of the present invention is to provide a xe2x80x9cplugxe2x80x9d, also known as a xe2x80x9ccollarxe2x80x9d, an xe2x80x9canchorexe2x80x9d, or a xe2x80x9cconexe2x80x9d, which satisfies some of the above-mentioned needs and is thus an improvement over the devices known in the prior art.
More particularly, the object of the present invention is to provide a new approach for operatively connecting torsion springs to overhead shafts of counterbalancing systems used for garage doors and the like.
In accordance with the present invention, the above object is achieved with a plug for use in a counterbalancing mechanism of a cable-operated door, said plug being mounted about an overhead shaft and used for operatively connecting said overhead shaft to a torsion spring coaxially mounted thereon, said plug comprising:
a cylindrical collar having opposite first and second portions, said collar being provided with a hooking slot for hooking a free end of the torsion spring therein and said torsion spring having a segment coaxially mounted about the first portion of the collar; and
a cylindrical flange rigidly affixed to the second portion of the collar, said flange being used for transferring a torque between the torsion spring and the overhead shaft when the flange is securely fixed about the overhead shaft;
wherein the plug further comprises a shouldering floor of a given length faced against the hooking slot and extending inside the collar, from the second portion towards the first portion thereof, between said collar and the overhead shaft.
Preferably, the collar is eccentrically mounted about the overhead shaft.
The objects, advantages and other features of the present invention will become more apparent upon reading of the following non-restrictive description of a preferred embodiment thereof, given for the purpose of exemplification only with reference to the accompanying drawings.